Ancient seed plant fossils reveal pollen-capture secret

BEIJING, March 26 (Xinhua) -- How did Earth's earliest seed plants capture pollen to reproduce? A team of scientists has uncovered new clues by studying 365-million-year-old seed plant fossils from China.

The discovery, led by researchers from Peking University and the Chinese Academy of Sciences' Nanjing Institute of Geology and Palaeontology, centers on a previously unknown seed plant species named Zaijunia biloba. The fossils, found in Changxing County, east China's Zhejiang Province, date back to the Late Devonian period, a time when early seed plants were just beginning to evolve.

Unlike ferns, which release spores into the environment, seed plants hold their female reproductive structures -- ovules -- on the plant itself. Capturing airborne pollen was crucial for their survival, but how these ancient plants managed it has long puzzled scientists.

Using advanced 3D modeling and airflow simulations, the team found that Zaijunia biloba's ovules had a clever design: four-lobed outer coverings that slowed down wind currents by about 91 percent. This allowed pollen grains to settle onto the ovules for fertilization.

The researchers also analyzed a more complex seed plant, which had cup-like structures surrounding its ovules. These reduced wind speed even more effectively -- 80 to 99 percent -- and worked equally well from all directions.

The findings, published in the latest issue of the journal Proceedings of the Royal Society B, highlight how early seed plants adapted to rely on wind for reproduction long before insects helped with pollination.

The study also shows how subtle changes in plant structure could make a huge difference in survival millions of years ago, said Xue Jinzhuang, an associate professor from Peking University.

The team plans to study more fossils to trace how pollen-capture strategies evolved over time. ■